There are an estimated 1.1 million survivors of colorectal cancer in the United States. Lifestyle practices including physical inactivity and poor dietary habits are risk factors for colorectal cancer incidence, recurrence, and mortality, and also increase the risk for other chronic illnesses. Most colorectal cancer survivors fail to engage in regular physical activity and do not meet recommendations for eating a healthy diet, including sufficient intake of fruits and vegetables and consumption of a low fat diet. However, cancer diagnosis may spur positive health behavior changes for some cancer survivors. Previous research has focused primarily on understanding health behavior changes made by breast cancer survivors. In contrast, the proposed research uses a comprehensive, theory-driven approach to understand the degree, predictors, and affective and cognitive effects of physical activity and dietary changes made by survivors of colorectal cancer, who represent a large but relatively understudied survivor population. The conceptual framework for the proposed research draws from social cognitive theory and the common-sense model of health and illness self-regulation. Individuals who recently finished treatment for localized or regional stage colorectal cancer will complete a comprehensive baseline survey, including assessments of their current physical activity and dietary practices, as well as relevant social cognitive and self-regulatory predictors. Participants will complete follow-up assessments 3 months and 6 months later, which will provide data on changes in physical activity and diet, as well as potential affective and cognitive effects of such behavior changes. Additionally, we will examine survivors'preferences regarding health promotion programs. Understanding the natural course and predictors of health behavior change is a proven approach for guiding effective interventions. An enhanced understanding of the social cognitive and self-regulatory causes, and affective and cognitive effects, of physical activity and dietary changes made by colorectal cancer survivors will inform the development of health behaviors interventions for this population. The development and dissemination of effective health behavior interventions has been highlighted as a key area for future cancer survivorship research. PUBLIC HEALTH RELEVANCE: In parallel with the increase in the cancer survivor population in the United States, there has been growing interest in helping cancer survivors to make positive health behavior changes. The proposed research examines the degree, predictors, and affective/cognitive effects of physical activity and dietary changes made by colorectal cancer survivors. The results of this research will inform the development of a behavioral intervention designed to increase physical activity and promote healthy dietary practices among colorectal cancer survivors.